Various portable devices, including wireless communications devices, utilize a portable energy source such as one or more batteries. Notwithstanding improvements to both battery technology and power consumption of such portable devices, batteries nevertheless represent a finite source of power. Ways to extend (indefinitely if possible) battery life are constantly being sought.
For some devices, solar cells represent a viable supplemental or alternative energy source. Some devices, such as portable calculators, have both sufficiently large available surface area and sufficiently low power needs that some of these devices can be powered entirely by one or more solar cells. Unfortunately, many devices, including for example cellular telephones and other wireless communications devices have both higher power demands and an often limited available surface area for locating a solar cell. As a result, solar cells have not been viewed as a satisfactory supplemental or alternative power source for such devices.
Some prior art suggestions have been made to combine a solar cell with a display such as a liquid crystal display. Such a combination seems attractive since the display will comprise an ordinary part of the device at issue and the solar cell itself would not require additional surface area. Unfortunately, prior art attempts in this regard have been unsatisfactory. In particular, light that finally reaches the active light receiving surface of the solar cell has been sufficiently attenuated as to substantially mitigate the quantity of electrical power that can be provided by the solar cell even under ideal conditions. The small incremental quantities of supplemental power provided through such prior art attempts have been too small to warrant the additional cost and complexity of providing such a combination in most if not all such devices.
Consequently, a continuing need exists for a way to supplement or replace battery power in portable devices including wireless communications devices in a commercially acceptable and cost-effective manner.